Cheers for the advice. Just 1 more quick question. Would you set up wired or a complete wireless network.(just the airport and the mini mac server controlling all) I have the option of both. The room will be used for photoshop editing etc.
Thanks again.
Somehow your topology seems a bit under par. Servers should control the desktops and as well their access to the network and Internet. That means your Mac Mini is in control of the desktops and the Airport is not. Skip wireless for the most part and connect via Cat 5e or 6 Ethernet. This is the fastest access they will get.
Security - you should consider a better firewall than the AE. Also, wired or wireless, use reserved DHCP for each machine. This is akin to giving them a DHCP counterpart to a static IP. Each user should have his/her own log in.
While I am a Mac fan, I never considered the AE as a good device for a router in a business or school. There are better alternatives that are more robust and with better admin tools.
Your list of equipment should be
Firewall
Router
switch
Mac Mini
desktops
Wireless option - always encrypted, again reserved DHCP. No GUEST access.
Consider access points or bridged AE's.
Some routers come with excellent firewalls built in (AE is not one of them).